I was tinkering around with XenServer the other day. I know I can hear you saying “is that a thing?” Well, it is, but this is not what I am going to talk about today. Time for a tangent shift. I thought I would have a look for a third-party switch for XenServer, but it seems that XenServer is a third-rate citizen in this space, as there is no Cisco Nexus 1kV available for XenServer, even though Cisco previewed it at Citrix Synergy Barcelona in 2012.
This got me thinking. Do you know how many virtual switches are available for your chosen hypervisor? Well, for vSphere, there is the standard virtual switch and one, two, maybe three distributed ones. I think you will be surprised at the answer. Have a little look at the table below:
|VMware vSphere||Red Hat KVM||Microsoft Hyper-V||Citrix XenServer|
|Standard/Single Host||All editions||Linux Bridge (Ebtables)||vSwitch||Linux Bridge (Ebtables)|
|Distributed Switch (multi-host)||Enterprise Plus (all editions supported by VSAN)||Open vSwitch||Open vSwitch|
|NSX Distributed Router||NSX vSwitch||Open vSwitch||Open vSwitch||Open vSwitch|
|Cisco||Cisco Nexus 1000V||Cisco Nexus 1000V||Cisco Nexus 1000V|
|Cisco||Application Virtual Switch|
|5nine||Extensions to Microsoft Virtual Switch|
|HP FlexFabric Virtual Switch 5900v||Needs Enterprise Plus
(only vSphere 5 and HP FlexFabric)
|IBM Distributed Virtual Switch 5000v||Needs Enterprise Plus
(only vSphere 5 and IBM 5000 switch)
As expected, vSphere has the most options, there being several choices—yes, that’s correct: seven virtual switches—followed by KVM, Hyper-V, and finally, bringing up the rear, XenServer.
vSphere has the built-in switches, both the standard, which is available in all editions, and the distributed version, which is available in Enterprise Plus. (Incidentally, you can gain access to the vDS as part of a VSAN purchase; however, there are some licensing hoops you need to jump through to correctly activate it.)
Red Hat KVM has two inbuilt options for virtual switching: the Linux “Ebtables,” which is effectively a bridged mode environment and akin to the VMware standard switch in form, and the Open vSwitch, for its distributed model of switch.
Microsoft only has a single built-in switch option, that being akin to the standard virtual switch, and XenServer has two, these being the Linux bridge (Ebtables) and Open vSwitch.
It is in third-party support that we can see the gaps in coverage begin to appear.
I am treating NSX as a third-party product. Yes, this is a VMware product; however, VMware does a multi-hypervisor aware version. This version utilizes Open vSwitch to enable other hypervisors to sample VMware’s particular flavor of SDN goodness. On the table, you can see that all major hypervisors are supported.
Next we move on to Cisco. As a company, it was the first to market with a third-party virtual switch, the Nexus 1000V. Hypervisor support has been extended to KVM and Hyper-V, but even through Cisco demoed the switch running on XenServer in 2012 at Citrix Synergy, there has to date been no actual release for purchase. Cisco also has a virtual switch called the Application Virtual Switch, which moves its ACI SDN product into the hypervisor. Currently, this is only supported on vSphere and is a direct response to VMware’s NSX product stepping on their toes, in what they consider their personal fiefdom.
Finally, there are two lesser-known products from HP and IBM. The HP switch is designed to overlay the vDS on vSphere and can only be utilized in conjunction with the 5900 range of physical HP switches. Further, I am unsure if it is supported on vSphere 6, as all the documentation stops at vSphere 5.5.
The entry regarding the IBM switch could be construed as slightly disingenuous, since as of the end of September 2013 it has been withdrawn from sale; however, it is entered here for completeness. Again, this switch was designed to work with the IBM switches that supported EVB. Although this product is no longer openly available for sale, its IP has been rolled into IBM’s SDN VE product set.
The only other third-party switch is a set of extensions for Hyper-V from a company called 5nine. This adds virtual firewall extensions to the standard Microsoft Virtual Switch as a part of its Hyper-V tool set.
I hope you liked this brief overview of the types of virtual switches available for your hypervisor of choice. Now, if you are wondering why there was nothing in here about Nutanix’s Acropolis hypervisor, this hypervisor is based on KVM, so my working assumption is that it will support the same options as the Red Hat KVM. However, I am sure that I will be informed by its denizens if I am incorrect.